Pressurized fluidized bed reactors are known, such as shown in U.S. Pat. No. 4,869,207. In those reactors, a pressure vessel containing the reactor chamber is kept at superatmospheric pressure, that is a pressure of 2 bar or more, and preferably at a pressure of about 8-16 bar (for the combustor), although the pressure varies substantially from one installation to another, or within an installation. A very significant cost of such pressurized reactors, however, is the pressure vessel itself, especially for circulating fluidized bed reactors which have a larger volume of solids than bubbling bed reactors. As the volume of the pressure vessel increases, the costs escalate in a geometric rather than linear manner. Therefore, it is desirable to maintain the pressure vessel at minimum size possible. However when the conventional cyclone separator is utilized with the reactor chamber within the pressure vessel, there is significant wasted space, and the pressure vessel must be made proportionately larger in order to accommodate a conventional cyclone. If the cyclone is placed outside the pressure vessel, then seals must be provided leading the hot flue gases from the reactor chamber to the cyclone separator, and also between the cyclone separator particles recirculating conduit and the reactor chamber.
The parent application includes a cyclone separator that is distinctly non-circular, typically having a quadrate cross-section of the vortex chamber or gas space therein. It has been found according to the present invention that when the distinctly non-circular cyclone separator, or a plurality thereof, are provided in association with a pressurized fluidized bed reactor, a much more compact arrangement is provided, allowing a minimum size of the pressure vessel, and thus allowing economic construction of a pressurized fluidized bed reactor that does not require seals for the cyclone separator since the cyclone separator may be mounted directly within the pressure vessel.
The compact arrangement of the cyclone separator in the pressurized fluidized bed reactor according to the present invention has still another advantage. Because of the compact nature thereof, there is additional room for other structures, for example allowing ceramic filter elements, such as ceramic candle or honeycomb filters, to be mounted in the same pressure vessel as the reactor chamber and the cyclone separator (e.g. below or above the cyclone separator), so that a second pressure vessel need not be provided for gas filtration, thereby reducing the costs of a complete system substantially.
According to the present invention, a pressurized fluidized bed reactor is provided comprising the following elements: A pressure vessel, circular in cross-section, and capable of withstanding pressures greater than 2 bar, and having a top and a bottom. Means for pressurizing the vessel to a pressure of greater than 2 bar. A reactor chamber defined within the pressure vessel including by side walls and a ceiling. Means for introducing fluidizing gas into the reactor chamber. Means for feeding fuel into the reactor chamber. Means for leading hot combustion gases away from the reactor chamber. And, a centrifugal separator disposed within the pressure vessel, and having an inlet connected to the means for leading hot combustion gases away from the reactor chamber, a gas outlet leading from the separator out of the pressure vessel, and a return duct for recirculating separated solid particles from the separator to the reactor chamber. The centrifugal separator comprises a vertical vortex chamber having distinctly non-cylindrical walls defining an interior gas space, the gas space having a cross section that is distinctly non-circular, having a circularity greater than or equal to 1.15.
The gas space typically has a quadrate cross-section, the cyclone separator made frown substantially flat panels.
The centrifugal separator may comprise a first centrifugal separator, and there may be a second centrifugal separator having the same basic components, as described above, as the first separator. Separators may be disposed on opposite sides of the reactor chamber, connected to the reactor chamber side walls, or may be disposed on the same side of the reactor chamber positioned next to each other or one above the other. If they are positioned one above the other, and if one separator gas outlet discharges upwardly, the other (the upper separator) preferably discharges downwardly so that there is a common plenum connected to the gas outlets. Multiple substantially identical separators may be provided mounted in groups (e.g. pairs) on opposite sides of the reactor chamber. The reactor chamber may have a first cross-sectional area, and each of the separators has a second cross-sectional area of the gas space thereof, and those cross-sectional areas may be substantially equal.
The means for pressurizing the pressure vessel may comprise means for introducing oxygen containing gas under pressure at the top of the vessel to pressurize the interior of, the pressurizing gas flow also comprising means for supplying fluidizing gas to the reactor chamber at the bottom thereof. Other pressurizing mechanisms may also be utilized. A plurality of omega panels may be provided in the reactor chamber extending along the length thereof and the separators may be mounted on the lengthway sides of the reactor chamber, parallel to the omega panels.
The reactor may further comprise a plurality of ceramic filtering means such as candle, monolithic, or honeycomb filters mounted in a support structure within the pressure vessel, and having a dirty gas inlet, a clean gas outlet, and an ash outlet; the dirty gas inlet connected to the separator gas outlet. The "ceramic filtering" as used in the specification and claims means conventional ceramic candle, monolithic, or honeycomb filters, or improved filters developed in the future, capable of filtering particles out of high temperature gases such as flue gases from fluidized bed reactors. A number of different arrangements may be utilized to accommodate the ceramic filtering means. In one arrangement, the separator is mounted along a side of the reactor chamber, connected to a side wall thereof, and the gas outlet is directed downwardly, and the support structure and the ceramic filtering means filters are mounted to the same side wall of the reactor chamber as the separator, beneath the separator, the filters of the filtering means extending generally horizontally.
According to another arrangement, the separator is mounted along a side of the reactor chamber, connected to a side wall thereof, the gas outlet is directed upwardly, and the support structure and the ceramic filtering means are mounted above the reactor chamber ceiling and above the separator. According to yet another arrangement, the separator is mounted within the volume defined by the reactor chamber, the gas outlet is directed upwardly, and the support structure and the ceramic filtering means are mounted above the reactor chamber ceiling and above the separator. Alternatively, candle or monolithic filters may be disposed vertically in the dirty gas inlet provided at a first side of the reactor chamber, and the ash outlet on the second opposite side of the reactor chamber, with a downwardly sloping floor extending from the first to the second sides. In this situation the candle or monolithic filters may be of different lengths, being short adjacent to the first side and longer adjacent to the second side.
It is the primary object of the present invention to provide a compact pressurized recirculating fluidized bed reactor with the cyclone separator or separators within the pressure vessel, and one which may also accommodate ceramic filtering means eliminating the need for a separate pressure vessel for the filters. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.